SOUTH LAKE TAHOE -- El Dorado County Sheriff's Sgt. Pete Van Arnum recalls hearing tales of Mafia members dumping bodies in Lake Tahoe back in the 1950s.

"That may or may not be true, but we can't be sure because we can't go down that far," said Van Arnum, a former coroner.

What, or whom, Lake Tahoe holds is a mystery, except for those who have lost family or friends in drownings, boating accidents or other fatal mishaps. The conditions within the lake, the nation's second-deepest at about 1,645 feet, keep the mystery unanswerable.

The recent discovery of a woman's body in shallow waters near Glenbrook, on the Nevada side of the lake, perplexed some who know how the lake keeps its victims.

"Usually a person who goes into the lake, they don't come back up," said Mike McFarlane of McFarlane Mortuary.

"I just never, never have seen anyone floating," he said. "They usually go down and that's it."

"We've had a number of cases over the years where drowning victims, or apparent drowning victims, never surfaced again," said El Dorado County Sheriff's Lt. Les Lovell. "They're just gone."

Las summer a man from India was reported by his friends to have drowned in water 700 feet deep after he fell into the lake off a flotation device. He was wearing a life vest, which was later found floating by itself. The case was filed as a missing person in case his body ever surfaces.

A number of factors contribute to the phenomenon of bodies not rising to the surface at Lake Tahoe, according to Dr. Anton Sohn, chairman of the pathology department at the University of Nevada, Reno.

When people drown, their lungs fill with water, dropping them into the depths of the lake. Decomposition starts, and during that process gases such as methane, nitrogen and oxygen are produced.

In warmer water, the gases would allow a body to rise "like a balloon. The body buoys up to the top," Sohn said. But since Lake Tahoe is so cold, bodies don't decompose, gases don't form, and the bodies stay submerged.

Lake Tahoe has a constant temperature of 39 degrees from the depths of 600 to 700 feet, according to the U.S. Geological Survey. Its surface temperature varies with the season. In August and September the surface temperature runs from 65 to 70 degrees. During the winter the surface temperature ranges from 40 degrees to 50 degrees.

A refrigerator at McFarlane Mortuary where bodies are kept to fight off decomposition is set at 34 degrees, McFarlane said.

Sohn added optimal temperatures for bacteria growth in laboratories is about 100 degrees. Cut that temperature in half and bacteria doesn't thrive, he said.

Van Arnum remembers the body of Lee Taylor, who died trying to break the water speed record on Lake Tahoe in November 1980. During a test run on the lake, Taylor's 40-foot-long, rocket-powered boat broke up and sank after reaching a speed of nearly 270 miles per hour.

Searchers used sonar devices and an underwater camera to spot an eight-foot section of the boat, with Taylor's body still strapped inside, at a depth of about 280 feet. A salvage crew used grappling hooks to haul the boat fuselage to the surface 10 days after the crash.

Taylor's body was "perfectly preserved," Van Arnum said.

Adding to the trouble of fetching bodies from the depths of the lake is the limited depth that divers can reach because of the lake's elevation, 6,225.5 feet above sea level.

At sea level, the recommended maximum depth for recreational divers with standard equipment is about 130 feet. But at Lake Tahoe, special tank mixtures are needed to exceed a maximum depth of 90 feet. Otherwise, a diver hits a dangerous, bends-inducing level.